Wednesday, 11 March 2009

This was another book that we picked up after a talk at the Bath Literature Festival. Of the four talks we attended, this was (for me, at least) the most interesting, as it covered a subject that I have long been interested in.

The book starts off with a piece of science fiction; an alien race coming back to visit Earth a few hundred million years in the future, only to find no trace of life - the entire surface of earth has essentially been wiped clean as the continents have reformed into one massive landmass. Only when the aliens turn their attention to the moon do they find traces of the race who once inhabited the planet below.

This is an interesting way of introducing this book on what is called 'deep time', or geologic time. In particular, it talks about how continental drift formed, then broke apart, one massive landmass on Earth. It also details how the current map of Earth that we all know is in transit, and how another large landmass will one day form. This cycle of the creation of a supercontinent which is then broken up, takes about 500 to 750 million years. It is the longest cycle in nature, longer even than the time it takes for the sun to revolve around the galaxy. As an aside, for maps of what past Earth and future Earth may look like, see the excellent www.scotese.com website.

That is one thing that needs noting about this book - the numbers mentioned are either very, very large, or infinitesimally tiny. As you read it, you are exploring things that are far away from our ordinary everyday understanding. Despite this, the information is presented in a way that is far from overwhelming.

The author outlines the botanical and geological reasons for believing that now-separated landmasses were once together, and goes into the theories that gained currency before continental drift, mainly involving the 'lost continents' of Atlantis, Lemuria and Mu (fans of the KLF can sing 'All bound for Mu Mu land' at that mention). It is a fascinating history, one that even includes Marie Stopes and Scott of the Antarctic.

There is a certain amount of humour in his writing, not least when the author discusses uniformitarianism (the concept that natural processes that operated in the past are the same as those that are observed today). He also details the conflict over Graham Bank, an island near Sicily whose tendency to rise out of the sea routinely causes diplomatic incidents as countries attempt to claim the land mass. Before it is all sorted out, it invariably sinks beneath the waves once more. This lightness of touch does much to improve the readability of what could otherwise have been a very dry academic text.

It also mentions the geology time charts that are so familiar. These charts outline the various geological epochs, and should be instantly recognisable to anyone who has done elementary geography. Right at the bottom, past the Cretaceous and the Jurassic, is the Precambrian, little more than a small, ill-regarded little sliver on the diagram. It is like this, so the author claims, because Precambrian rocks have very few fossils - it was before complex life had evolved. Later bands (such as the Jurassic) can be classified by the lifeforms within them. Earlier ones cannot. This led all those early rocks to be rolled up into one big 'precambrian' chunk.

Only now, scientists realise that 88% of the Earth's history is contained within that chunk. The rest, that long list of names of familiar names, takes up only 542 million years, or just 12% of our planet's life. Later chapters in this book details some of the ways that geologists are attempting to uncover what the Earth was like in those ancient times.

Two timely lessons are embedded in this book; one is that the consensus in science can be wrong, and that scientists will fight very hard to keep that consensus despite the evidence. Both of these are embodied in the way that many geologists and geophysicists declined to believe in the theory of continental drift, despite the ever-increasing body of evidence for it.

Perhaps the most interesting part of the book is when he talked about snowball earth, the time when the entirety of the earth's surface was covered by thick layers of ice. I have always had some problems with this idea, and the author explains the situation far more clearly than the several TV programs I have seen on the matter. He also takes time to display some of the counter arguments against the controversial theory.

The book started with a fiction, and ends with a tragic fact. It ends with a description of the 2004 Asian Tsunami, and the author then makes an eloquent case not just for his science, but all science:

If today there is fresh water on Namibian farms and in Vienna, and an emerging tsunami early-warning system in the Indian Ocean, it is because geologists in the past have done the science that brings a closer understanding of deep time and the inner workings of the Earth. You cannot pick and chose with science. A seemingly rarefied geology that reconstructs the lost supercontinents of Earth's deep past is the same science that (with political will) can save hundreds of thousands of lives in the Indian Ocean when the next tsunami strikes. The arcane business of how our Earth's atmosphere evolved during the Precambrian under the influence of evolving life is the same science that helped us understand the massive, uncontrolled climate experiment in which the human race is currently engaged. But to deny one part of science is to deny it all. Science hangs together. It is a supercontinent.

If you want a detailed introduction to plate tectonics and deep time, then this could be just the book for you. It is very readable, and is (for a science book) fairly accessible. I would give it 5 out of 5, as the author has managed to make a subject that is often impenetrable understandable.